Safety appliance for air-brakes.



No. s7|,201. Patented A r. 2, 19m.

A. COWPERTHWAIT.

SAFETY APPLIANCE BOB AIR BRAKES.

(Applipation filed Feb. 4, 1901.)

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lJNTTEo STATES PATENT OFFICE.

ALLAN COWPERTl-IWAIT, ()F BROOKLYN, NEW YORK, ASSIGNOR TO ALONZO B. SEEAND WALTER L. TYLER, OF SAME PLACE.

SAFETY APPLIANCE FOR AIR-BRAKES.

SPECIFICATION forming part of Letters Patent No. 671,207, dated April 2,1901.

Application filed February 4, 1901- Serial No. 45,826. (No model.)

it) rd/Z whom it may con/Jere:

Re i 1: known that I, ALLAN COWPERTHVVAIT, a citizen of the UnitedStates, residing at the city of New York, in the borough of Brooklyn andState of New York, have invented certain new and useful Improvements inSafety Appliances for Air-Brakes, of which the following a full, clear,and exact description.

This invention relates to air brakes in which a piston is moved acertain distance to apply the brake shoe or strap by the pressure of airadmitted to the cylinder in which the piston plays. As the brake shoe orstrap is subjected to considerable wear, the stroke of the pistonnecessarily varies, it being least when new shoes or straps are in useand greatest when the shoes or straps have been a long time in service.In some constructions of brake apparatus the stroke of the piston has apredetermined length, and when the wear on the shoe or strap has becomeexcessive it sometimes happens that the piston will complete its strokebefore the shoe or strap can grip the shaft sufficiently to bring it toa stop Within the proper time. For elevator purposes it is absolutelyessential that the brake shall be efficient at all times, and anyconstruction which would permit the powershaft to rotate after the brakehas been applied would not be permissible.

The object of my invention is to provide means whereby the motive powerwhich 0perates an elevator shall be made inoperative whenever the wearupon the brake shoe or strap becomes so great that the brake can nolonger act with its normal efficiency. The elevator to which myapparatus is applied is electrically driven and the inotoris supposed tocontrol the shaft positively whether the car is going up or down andregardless of the counterbalancing of the car, so that when the motor isstopped the elevator is necessarily stopped. The function of my improvedapparatus is to stop the motor or to open a circuit controlling themotor whenever the wear on the brake shoe or strap becomes excessive orwhen it is so great as to require renewal of the friction-surface.

My invention will be described with reference to the accompanyingdrawings, in which-- Figure l is a conventional representation of abrake and a power-cylinder fitted with my improved apparatus, and Fig. 2is a plan of the cylinder.

A represents a disk or drum upon one of the shafts through which thepower is transmitted. It is surrounded by a brake of usual constructionconsisting of straps a and a, hinged together at a and connected,respectively, to the opposite ends of a short lever a pivoted at itsmiddle point. The straps are each provided with leather or othersuitable working faces 0 which make contact with the periphery of thedisk, and thus are subjected to wear. The lever a is connected at itspivot with another lever 12. which in turn is connected with the end ofa pistonrod 1) in such a manner that the reciprocations of the rod willcause the brake-straps to approach or recede from the rim of the disk.The piston-rod is connected with a piston (not shown) located in apower-cylinder O. This cylinder is of large diameter and short length,so as to afford great pressure through a short stroke. e and e are twoelectrical contacts in a circuit controlling said motor. The contactsare normally bridged and the circuit maintained by a connecting-plate f,carried by a lever g, pivoted at g. The axis of this lever is surroundedby a torsion-spring 9 which tends to swing the lever to one side andcarry the plate f out of connection with the contacts 6 e. The spring isprevented from accomplishing this normally by a retaining-bar h, whichis provided with an offset or extension piece it, resting against thefree end of lever g. The bar his parallel to the side of the cylinder,but extends beyond the head of the same and connects with the transversearm 2', bolted to the piston-rod b. The bar 7L therefore rises and fallswith the piston-rod, and the offset on the bar slides along the free endof the lever g. The extent of. the contact between the lever g and theextension h is so related to the stroke of the pistonin the cylinderthat so long as said stroke is of the normal length the extension h willnever go beyond the end of lever g, and will thus act as a lock to holdthe plate f in connection with the contacts 6 6; but when the wear ofthe contact material a on the brake-straps exceeds a predeterminedamount the stroke of the piston thereby becomes longer and the extensionh passes entirely beyond the end of lever g, thus permitting the springg to act and quickly throw the lever to one side. This opens thecontrol-circuit of the motor by disconnecting the contacts e', and thedriving-motor cannot thereafter be started until the connecting-platefhas been replaced, which obviously will not be done until thefriction-surfaces a of the brake have been renewed.

Having described my invention, I claim 1. In an air-brake, thecombination of a brake shoe or strap, a piston adapted to operate thesame, an electric controlling-circuit, and means whereby the length oftravel of the piston will determine the continuity of said circuit.

2. In an air-brake, the combination of a brake shoe or strap, a pistonadapted to opcrate the same, an electric controlling-circuit, a cut-outin said circuit and means whereby the cut-out will be locked in itsclosed position while the stroke of the piston is normal, and unlockedwhen the stroke becomes abnormal.

3. In an air-brake, the combination of a brake shoe or strap, a pistonadapted to operate the same, an electric con trolling-circuit, a cut-outlever controlling said circuit, an arm connected with said piston andnormally bearing against said cut-out lever, but adapted to pass beyondthe lever when the piston makes an abnormal stroke, and means for movingsaid cut-out lever when the piston releases it.

In witness whereof I subscribe my signature in presence of twowitnesses.

ALLAN OOWPERTI'HVAIT.

Witnesses:

WM. A. RosENBAUM, WALDo M. OHAPIN.

